Embodiments of the present invention relate to a positive-intrinsic-negative (PIN) or negative-intrinsic-positive (NIP) diode and a method for manufacturing a PIN/NIP diode, and more particularly, to a PIN/NIP diode having at least one trench and a method for manufacturing a PIN/NIP diode having at least one trench.
Positive-intrinsic-negative (PIN) diodes or PIN photodiodes are generally known in the art. A PIN diode is a type of photodiode with a large, neutrally doped intrinsic region sandwiched between p-doped and n-doped semiconducting regions. The PIN diode's name comes from the layering of these materials positive, intrinsic, negative (PIN). Broadly speaking, a photodiode is a semiconductor device that converts light to electrical current. A PIN diode typically exhibits an increase in its electrical conductivity as a function of the intensity, wavelength, and modulation rate of the incident radiation.
A PIN diode is also a semiconductor device that operates as a variable resistor at radiofrequency (RF) and microwave frequencies. The resistance value of the PIN diode is determined only by the forward biased direct current (DC) current. At high RF frequencies when a PIN diode is at zero or reverse bias, it appears as a parallel plate capacitor, essentially independent of reverse voltage.
FIG. 3 depicts a partial cross-sectional elevational view of a conventional planar PIN diode 510. A lightly doped intrinsic layer 516 separates more heavily doped p-type and n-type layers 514, 518 which function as anode and cathode, respectively. The sensor surface 516a is typically coated with an oxide or nitride passivation layer 512.
A PIN diode's effectiveness is related to the depletion region (i.e., the active detection area of the PIN diode). When a depletion area of a PIN diode is small, many electron-hole pairs recombine before they can create a current in the external circuit. Both the sensitivity and the output current are proportional to the depletion area. Accordingly, it is desirable to make the depletion region as large as possible.
It is desirable to provide a PIN/NIP diode having an increased effective surface area per unit area of device physical surface area. Further, it is desirable to provide a PIN/NIP diode having at least one trench.